S72-40822 (21 April 1972) --- A color enhancement of a far ultraviolet photograph showing the geocorona, a halo of low density hydrogen which surrounds our planet. The light which produced this picture had a wavelength of 1,215 angstrom, about one-third the wavelength of the bluest light visible to the naked eye. Hold photo with open part of crescent facing right. The region artificially reproduced in red here is the faint hydrogen glow and other regions of the same brightness in the original black and white photograph. The spike on lower right is auroral activity over the south magnetic pole, and other light scattered by Earth's atmosphere covers part of the dark side of Earth. The blue background represents black sky around Earth. The original photograph was taken by astronaut John W. Young, Apollo 16 commander, during the mission's first extravehicular activity (EVA) on April 21, 1972. The UV camera was designed and built at the Naval Research Laboratory, Washington, D.C. Please note the original onboard photograph number for this photo is AS16-123-19652.